A New Evaluation Method of CO2 Storage Capacity in Coalbed Reservoirs

Carbon Capture Utilization and Storage (CCUS) is playing a significant role in dealing with the global climate change. In order to study CO₂ storage capacity in coalbed reservoirs, adsorption/desorption experiments of coal rocks from different regions and coal ranks are conducted. Experimental results show that laws of desorption and absorption for two different coal ranks are obviously different and CO₂/CH₄ adsorption ratio is different along with reservoir depth. This paper points out weaknesses of evaluation methods in existing models, shows clearly what problems existing in the previous methodologies and regards the proved ratio is a key factor when evaluation. Various factors are taken into account in the new evaluation method including proved ratio, replacement ratio of CO₂ to CH₄, recovery ratio, ash content and moisture, completion factor, efficient pores volume, gas saturation and so on. Therefore, it is the first time to clearly put forward storage depth limitation. In addition, new methods for evaluating theoretical, effective, practical and matched capacity are proposed. Also, reasonable depth of CO₂ storage is determined in China according to present production technology. Finally, this paper expresses evaluation results of CO₂ storage capacity in China’s coalbed reservoirs which prove the applicability of new methodologies.